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1

Saturday, June 21st 2008, 9:13am

SF/LF-155 Design

Here's a small design for a 155-ton, 19 knot coastal craft. They can be built as ulltralight minesweepers (SF-class) or as subchasers (LF-class). Specs are the same for both at the moment.

The design is pretty much identical to the Minenräumboot of WWII, but a little broader in the beam. Rather longlegged for a boat of her size, but it helped stability a bit.

SF/LF-155t, Irish Subchaser/Light Minesweeper laid down 1936

Displacement:
141 t light; 145 t standard; 155 t normal; 163 t full load

Dimensions: Length overall / water x beam x draught
134.51 ft / 134.51 ft x 19.36 ft x 5.58 ft (normal load)
41.00 m / 41.00 m x 5.90 m x 1.70 m

Armament:
1 - 1.57" / 40.0 mm guns in single mounts, 1.95lbs / 0.89kg shells, 1936 Model
Anti-aircraft gun in deck mount
on centreline forward
3 - 0.79" / 20.0 mm guns in single mounts, 0.24lbs / 0.11kg shells, 1936 Model
Anti-aircraft guns in deck mounts
on side, all amidships
Weight of broadside 3 lbs / 1 kg
Shells per gun, main battery: 350

Machinery:
Diesel Internal combustion motors,
Geared drive, 2 shafts, 1,439 shp / 1,073 Kw = 19.00 kts
Range 2,500nm at 10.00 kts
Bunker at max displacement = 19 tons

Complement:
21 - 28

Cost:
£0.057 million / $0.229 million

Distribution of weights at normal displacement:
Armament: 0 tons, 0.2 %
Machinery: 40 tons, 26.0 %
Hull, fittings & equipment: 80 tons, 51.7 %
Fuel, ammunition & stores: 14 tons, 9.2 %
Miscellaneous weights: 20 tons, 12.9 %

Overall survivability and seakeeping ability:
Survivability (Non-critical penetrating hits needed to sink ship):
293 lbs / 133 Kg = 150.2 x 1.6 " / 40 mm shells or 0.3 torpedoes
Stability (Unstable if below 1.00): 1.13
Metacentric height 0.5 ft / 0.2 m
Roll period: 11.1 seconds
Steadiness - As gun platform (Average = 50 %): 52 %
- Recoil effect (Restricted arc if above 1.00): 0.02
Seaboat quality (Average = 1.00): 1.53

Hull form characteristics:
Hull has a flush deck
Block coefficient: 0.374
Length to Beam Ratio: 6.95 : 1
'Natural speed' for length: 11.60 kts
Power going to wave formation at top speed: 65 %
Trim (Max stability = 0, Max steadiness = 100): 34
Bow angle (Positive = bow angles forward): 0.00 degrees
Stern overhang: 0.00 ft / 0.00 m
Freeboard (% = measuring location as a percentage of overall length):
- Stem: 11.48 ft / 3.50 m
- Forecastle (20 %): 9.84 ft / 3.00 m
- Mid (50 %): 9.02 ft / 2.75 m
- Quarterdeck (15 %): 8.20 ft / 2.50 m
- Stern: 8.20 ft / 2.50 m
- Average freeboard: 9.17 ft / 2.80 m
Ship tends to be wet forward

Ship space, strength and comments:
Space - Hull below water (magazines/engines, low = better): 100.9 %
- Above water (accommodation/working, high = better): 129.2 %
Waterplane Area: 1,584 Square feet or 147 Square metres
Displacement factor (Displacement / loading): 150 %
Structure weight / hull surface area: 24 lbs/sq ft or 119 Kg/sq metre
Hull strength (Relative):
- Cross-sectional: 0.79
- Longitudinal: 8.42
- Overall: 1.00
Hull space for machinery, storage, compartmentation is adequate
Room for accommodation and workspaces is excellent
Excellent seaboat, comfortable, can fire her guns in the heaviest weather

-20t for depth charges (LF-class)
-20t for minesweeping gear (SF-class)

2

Sunday, June 22nd 2008, 7:28pm

No comments? :( ;( :P

3

Sunday, June 22nd 2008, 7:57pm

No comments = Excellent design.

:D

... maybe a few more AA shells for the 40mm gun...
... and a BC >0.38...

4

Sunday, June 22nd 2008, 8:01pm

Quoted

Originally posted by Rooijen10
... and a BC >0.38...

Oh, bugger! That always sneaks back in somehow...
*Goes away muttering*

5

Sunday, June 22nd 2008, 8:07pm

There! Fixed it. Since I then had a tad bit of strength to burn I added some armor to protect the gunners...

Quoted

SF/LF, 158-Ton Type, Irish Subchaser/Light Minesweeper laid down 1936

Displacement:
143 t light; 147 t standard; 158 t normal; 166 t full load

Dimensions: Length overall / water x beam x draught
134.51 ft / 134.51 ft x 19.36 ft x 5.58 ft (normal load)
41.00 m / 41.00 m x 5.90 m x 1.70 m

Armament:
1 - 1.57" / 40.0 mm guns in single mounts, 1.95lbs / 0.88kg shells, 1936 Model
Anti-aircraft gun in deck mount
on centreline forward
3 - 0.79" / 20.0 mm guns in single mounts, 0.24lbs / 0.11kg shells, 1936 Model
Anti-aircraft guns in deck mounts
on side, all amidships
Weight of broadside 3 lbs / 1 kg
Shells per gun, main battery: 650

Armour:
- Gun armour: Face (max) Other gunhouse (avg) Barbette/hoist (max)
Main: 0.50" / 13 mm 0.50" / 13 mm -
2nd: 0.50" / 13 mm - -

- Conning tower: 0.50" / 13 mm

Machinery:
Diesel Internal combustion motors,
Geared drive, 2 shafts, 1,461 shp / 1,090 Kw = 19.00 kts
Range 2,500nm at 10.00 kts
Bunker at max displacement = 19 tons

Complement:
21 - 28

Cost:
£0.058 million / $0.232 million

Distribution of weights at normal displacement:
Armament: 0 tons, 0.2 %
Armour: 1 tons, 0.6 %
- Belts: 0 tons, 0.0 %
- Torpedo bulkhead: 0 tons, 0.0 %
- Armament: 1 tons, 0.4 %
- Armour Deck: 0 tons, 0.0 %
- Conning Tower: 0 tons, 0.2 %
Machinery: 41 tons, 26.0 %
Hull, fittings & equipment: 80 tons, 51.0 %
Fuel, ammunition & stores: 15 tons, 9.5 %
Miscellaneous weights: 20 tons, 12.7 %

Overall survivability and seakeeping ability:
Survivability (Non-critical penetrating hits needed to sink ship):
296 lbs / 134 Kg = 151.5 x 1.6 " / 40 mm shells or 0.3 torpedoes
Stability (Unstable if below 1.00): 1.14
Metacentric height 0.5 ft / 0.2 m
Roll period: 11.0 seconds
Steadiness - As gun platform (Average = 50 %): 51 %
- Recoil effect (Restricted arc if above 1.00): 0.02
Seaboat quality (Average = 1.00): 1.51

Hull form characteristics:
Hull has a flush deck
Block coefficient: 0.380
Length to Beam Ratio: 6.95 : 1
'Natural speed' for length: 11.60 kts
Power going to wave formation at top speed: 65 %
Trim (Max stability = 0, Max steadiness = 100): 34
Bow angle (Positive = bow angles forward): 0.00 degrees
Stern overhang: 0.00 ft / 0.00 m
Freeboard (% = measuring location as a percentage of overall length):
- Stem: 11.48 ft / 3.50 m
- Forecastle (20 %): 9.84 ft / 3.00 m
- Mid (50 %): 9.02 ft / 2.75 m
- Quarterdeck (15 %): 8.20 ft / 2.50 m
- Stern: 8.20 ft / 2.50 m
- Average freeboard: 9.17 ft / 2.80 m
Ship tends to be wet forward

Ship space, strength and comments:
Space - Hull below water (magazines/engines, low = better): 100.9 %
- Above water (accommodation/working, high = better): 129.5 %
Waterplane Area: 1,588 Square feet or 147 Square metres
Displacement factor (Displacement / loading): 149 %
Structure weight / hull surface area: 24 lbs/sq ft or 119 Kg/sq metre
Hull strength (Relative):
- Cross-sectional: 0.79
- Longitudinal: 8.30
- Overall: 1.00
Hull space for machinery, storage, compartmentation is adequate
Room for accommodation and workspaces is excellent
Excellent seaboat, comfortable, can fire her guns in the heaviest weather

-20t for depth charges (LF-class)
-20t for minesweeping gear (SF-class)

This post has been edited 1 times, last edit by "Brockpaine" (Jun 22nd 2008, 8:07pm)


6

Sunday, June 22nd 2008, 8:08pm

Quoted

Originally posted by Brockpaine
No comments? :( ;( :P


It happens every now and again......

Just one comment on an otherwise fine design, with the " Ship tends to be wet forward" warning, she is going to be hammered by Irish conditions.

I appreciate that the springsharp report says that is alright, it's just local knowledge!!!

7

Sunday, June 22nd 2008, 8:16pm

Modified again to give a higher forward freeboard.

Quoted

SF/LF-164t, Irish Subchaser/Light Minesweeper laid down 1936

Displacement:
149 t light; 153 t standard; 164 t normal; 173 t full load

Dimensions: Length overall / water x beam x draught
134.51 ft / 134.51 ft x 19.36 ft x 5.58 ft (normal load)
41.00 m / 41.00 m x 5.90 m x 1.70 m

Armament:
1 - 1.57" / 40.0 mm guns in single mounts, 1.95lbs / 0.88kg shells, 1936 Model
Anti-aircraft gun in deck mount
on centreline forward
3 - 0.79" / 20.0 mm guns in single mounts, 0.24lbs / 0.11kg shells, 1936 Model
Anti-aircraft guns in deck mounts
on side, all amidships
Weight of broadside 3 lbs / 1 kg
Shells per gun, main battery: 650

Armour:
- Gun armour: Face (max) Other gunhouse (avg) Barbette/hoist (max)
Main: 0.50" / 13 mm 0.50" / 13 mm -
2nd: 0.50" / 13 mm - -

- Conning tower: 0.50" / 13 mm

Machinery:
Diesel Internal combustion motors,
Geared drive, 2 shafts, 1,514 shp / 1,129 Kw = 19.00 kts
Range 2,500nm at 10.00 kts
Bunker at max displacement = 19 tons

Complement:
22 - 29

Cost:
£0.060 million / $0.241 million

Distribution of weights at normal displacement:
Armament: 0 tons, 0.2 %
Armour: 1 tons, 0.6 %
- Belts: 0 tons, 0.0 %
- Torpedo bulkhead: 0 tons, 0.0 %
- Armament: 1 tons, 0.4 %
- Armour Deck: 0 tons, 0.0 %
- Conning Tower: 0 tons, 0.2 %
Machinery: 42 tons, 25.9 %
Hull, fittings & equipment: 85 tons, 51.7 %
Fuel, ammunition & stores: 15 tons, 9.4 %
Miscellaneous weights: 20 tons, 12.2 %

Overall survivability and seakeeping ability:
Survivability (Non-critical penetrating hits needed to sink ship):
310 lbs / 141 Kg = 158.7 x 1.6 " / 40 mm shells or 0.3 torpedoes
Stability (Unstable if below 1.00): 1.11
Metacentric height 0.5 ft / 0.2 m
Roll period: 11.3 seconds
Steadiness - As gun platform (Average = 50 %): 55 %
- Recoil effect (Restricted arc if above 1.00): 0.02
Seaboat quality (Average = 1.00): 1.63

Hull form characteristics:
Hull has a flush deck
Block coefficient: 0.395
Length to Beam Ratio: 6.95 : 1
'Natural speed' for length: 11.60 kts
Power going to wave formation at top speed: 66 %
Trim (Max stability = 0, Max steadiness = 100): 34
Bow angle (Positive = bow angles forward): 0.00 degrees
Stern overhang: 0.00 ft / 0.00 m
Freeboard (% = measuring location as a percentage of overall length):
- Stem: 13.12 ft / 4.00 m
- Forecastle (20 %): 11.48 ft / 3.50 m
- Mid (50 %): 9.02 ft / 2.75 m
- Quarterdeck (15 %): 8.20 ft / 2.50 m
- Stern: 8.20 ft / 2.50 m
- Average freeboard: 9.75 ft / 2.97 m

Ship space, strength and comments:
Space - Hull below water (magazines/engines, low = better): 100.1 %
- Above water (accommodation/working, high = better): 129.7 %
Waterplane Area: 1,598 Square feet or 148 Square metres
Displacement factor (Displacement / loading): 151 %
Structure weight / hull surface area: 24 lbs/sq ft or 118 Kg/sq metre
Hull strength (Relative):
- Cross-sectional: 0.77
- Longitudinal: 10.01
- Overall: 1.00
Hull space for machinery, storage, compartmentation is adequate
Room for accommodation and workspaces is excellent
Excellent seaboat, comfortable, can fire her guns in the heaviest weather

-20t for depth charges (LF-class)
-20t for minesweeping gear (SF-class)

8

Sunday, June 22nd 2008, 9:20pm

Could be something for Persia, especially a Minelayer version

9

Sunday, June 22nd 2008, 10:26pm

Quoted

Originally posted by Rooijen10

Quoted

Originally posted by Brockpaine
No comments? :( ;( :P


No comments = Excellent design.

:D

I'd be careful on that assumption...a few of my designs got past with 'no comment', only to be picked apart after I'd already built 4 or 8 of 'em...

10

Sunday, June 22nd 2008, 10:31pm

Quoted

Originally posted by ShinRa_Inc
I'd be careful on that assumption...a few of my designs got past with 'no comment', only to be picked apart after I'd already built 4 or 8 of 'em...

A bit like my original Struma-class minesweepers. Posted them, got good comments, built three of them, THEN was told that transom sterns on mine warfare vessels are BAAAAD!

...thus, I now have a nascent design called the Struma II or Veleka-class, which I'll be building more of rather shortly...